Removal of aqueous selenium by four aquatic plants.

Several aquatic species were examined as potential phyto-removal agents for selenium in aqueous solutions. Selenium was initially present in concentrations of 0-100 ppm Se (as sodium selenite) in 10% Hoagland’s medium, and aquatic plants were grown in the medium for one week. Four aquatic plants were studied: Cattail (Typha domingensis), duckweed (Lemna obscura), hydrilla (Hydrilla verticillata Royle), and swamp lily (Crinum americanum). Analyses were done by atomic absorption spectrometry using hydride reduction. Four replicates were done for each analysis. Each system was examined for change in fresh weight, percent removal of selenium from solution, and accumulation of selenium in the plant. At selenium concentrations of 100 ppm or less, fairly good to excellent removal was achieved (65 to 100%), depending on the plant. Exposure to concentrations greater than 100 ppm had an inhibitory effect on plant growth, so concentrations less than 100 were studied in more detail. During a one-week period, hydrilla quantitatively removed the selenium, and the fresh weight and dry weights of the plant increased. Other plants were less effective in removal of selenium or were more adversely affected by added selenium.